The 9,000 hectare Tangkoko Nature Reserve is home to some of the most unique species in the world, such as the smallest primate - the Tarsier Spectrum - and the Black Crested Macaque, which is found only in North Sulawesi. There are, of course, birds such as the hornbill as well.
The park can be visited as a day trip from Manado, but it is a two to three hour drive there, and back, so if you really want to see the wildlife, an overnight trip is highly recommended, especially if you want to see the Tarsiers, since they are nocturnal. Manado-based Safari Tours can arrange either a day trip or an overnight home stay. The Pulisan Resort on the coast within the reserve is also a good option if you would like to spend some time in the area.